Drug dependency is extremely difficult to escape. This is true whether the dependency is one based on ethanol, amphetamine, barbiturates, benzodiazepines, cocaine, nicotine, opioids, and phencyclidine or the like. There is a need, therefore for an agent decreasing or overcoming such addiction and, if possible reducing or eliminating the symptoms related to the withdrawal of such drugs or substances of abuse.
Different classes of neuronal receptors and neurotransmitters in the brain have been implicated in the complex mechanisms underlying for example the compulsive drinking of alcohol. Experimental findings have favoured the opioid, dopaminergic, serotonergic, and benzodiazepine receptor subtypes.
Based upon a large number of genetic and pharmacological studies, serotonin (5-ET) containing neurons in the limbic-midbrain and limbic-forebrain pathways are seemingly involved, in part, in the fundamental mechanisms underlying for example alcohol drinking.
A number of reports have established that 5-HT uptake blockers significantly attenuate ethanol intake in rats. For example, zimelidine (The Merck Index 11th Ed., No. 10024) was found to have a potent inhibitory effect on voluntary ethanol consumption in rats. In human trials, zimelidine was shown to increase the number of abstinent days and to produce a slight reduction in the number of daily drinks. There is ample evidence that serotonin is involved in the regulation of both food and fluid intake. Zimelidine was found to attenuate the ingestion of food and alcohol concomitantly. It is possible, therefore, that zimelidine's action is mediated through more global effects on consummatory behaviour rather than specific effects on ethanol reinforcement.
Buspirone (The Merck Index 11th Ed., No. 1493), a partial 5-HT.sub.1A agonist, has been found to be effective for the treatment of anxiety. Buspirone was reported to attenuate significantly the consumption of alcohol by monkeys. In a clinical trial comparing buspirone to placebo in alcohol-dependent individuals, there was a lower drop-out rate in the buspirone-treated group, which also reported fewer signs of craving.
Amperozide (The Merck Index 11th Ed., No. 612), a 5-HT.sub.2 antagonist, was reported to significantly attenuate the intake of alcohol in rats without affecting neither consumption of food nor level of body weight.